1. Field of the Invention
The invention relates to a magnetic resonance imaging apparatus, and particularly to a multipurpose dedicated imaging apparatus having improved features for imaging the region of the vertebral column.
2. Description of the Related Art
Imaging the vertebral column may require the possibility of bringing the patient in an upright position in order to have the vertebral column loaded by the weight of the patient. In the normal laying down position of the patient on a bed or table having an horizontal orientation, the vertebral column will be in an unloaded and ideal condition. Thus, most pathologies may not arise clearly and the examination will lead to unclear results or to negative results despite the fact that the patient is showing typical symptoms of a disease of the vertebral column.
Actually known magnetic resonance imaging apparati use so called total body scanners which magnetic structure houses the entire body or a considerable part of it inside the patient examining space defined by the magnetic structure.
U.S. Pat. Nos. 6,414,490 and 6,504,371 disclose magnetic resonance imaging apparatus of the above mentioned kind. The magnetic structure is designed to generate a horizontal magnetic field. The patient is brought inside the examining space by means of a patient positioning device which is a bed or table mounted on a carriage, which bed or table can be further tilted around horizontal axis for giving different orientations to the bed or table with respect to the vertical direction. Furthermore, in order to focus the region of the patient to be imaged, the bed or table or carriage may be associated with an elevator which displaces the patient up and down relative to the examining space between the poles of the magnetic structure.
The actual devices are very big, heavy, and expensive. Big and heavy magnetic structures have problems of installation, since the room where the imaging apparatus has to be installed must necessarily have a floor which can support the weight of the imaging apparatus. Furthermore, the room must be sufficiently big to permit installation.
The patient positioning device is also relatively expensive due to the tiltable or swingable bed or table and due to the necessity of an elevator for displacing the patient relative to the imaging space in the magnetic structure.
On the other hand, even if the anatomic region of the vertebral column is a very large one, usually examination through imaging is carried out for only a certain specific part of the vertebral column.